The present invention relates to an optical lens structure and a means of manufacturing the same wherein the optical lens reflects light in a manner that is scattered while allowing a portion of the light striking the lens surface to pass through the lens in a coherent manner similar to that of a conventional eyeglass lens.
The basic theory behind a lens structure of this type is simply that a transparent medium, such as a window pane, will transmit light in a coherent or undistorted manner provided that both surfaces of the window pane, which are perpendicular to the light rays, are optically smooth and parallel to one another. If, however, one of the two surfaces is not optically smooth, that is to say, etched, scratched or sculptured in some manner, the light passing through the transparent medium will be distorted. Generally speaking, the more the surfaces are etched, the more the transmitted light will be distorted. This basic phenomena is commonly applied to the design glass of acrylic shower doors in which one side of the glass is typically textured while the other side remains smooth, the result being that an observer cannot clearly see through the shower door.
The texturing of the shower door, as described above, causes the light to be distorted simply because the refractive index of the transparent medium, such as glass, is different than that of air. In other words, the speed at which light travels through air is different than the speed at which light travels through glass. The fact that the speed of light will change as a function of the medium through which it is traveling is pertinent in that, on a microscopic level, as the light rays pass through an uneven surface of one transparent medium, the light rays will exit that transparent medium at slightly different times. This will cause the light rays that were previously moving together at the same rate to change speeds at slightly different times, in turn causing the light rays to become scattered.
A textured surface, as described above, is in effect made up of peaks and valleys. Such a surface is commonly referred to as a "relief pattern." It is those peaks and valleys that cause the once coherent light rays to exit the transparent medium at different times, resulting in distortion. If another transparent medium, such as a liquid, for instance, having exactly the same refractive index as the glass, is applied to the textured surface of the glass (the side opposite the textured side of the glass being optically smooth), such that the liquid fills in the peaks and valleys of the textured surface, in turn providing an optically smooth surface, the light will once again pass through without distortion. If the refractive index of the liquid is the least bit different than that of the glass, the light will remain distorted. The degree to which the light remains distorted is directly proportional to the mismatch in refractive indices between the glass and the liquid. For example, water on the etched surface of a shower door will cause the door to become more transparent yet not as clear as a window pane, for example. The shower door does not become perfectly clear basically because water does not have the same refractive index as glass. However, the refractive index of water is closer to that of glass than the refractive index of air is to glass, and that is why the door becomes more clear. It is important to note that nearly every different type of transparent medium will have a unique refractive index.
Consider again a light transmitting substrate in which a first side of the substrate is opticaly smooth and a second side is textured. If a vacuum deposited reflective type coating, like the type of coatings used to create a mirrored sunglass lens, is applied to the textured side of the light transmitting substrate, the reflective coating will highlight the textured surface. Consider now an optically clear liquid applied to the reflective coated textured surface in which the liquid fills in the peaks and valleys of the textured surface and is made to provide a new surface which is optically smooth and parallel to the first side of the substrate. If the liquid has exactly the same refractive index as the transparent substrate, the newly constructed multi-layered substrate will once again allow light to pass through undistorted. At the same time, the reflective coating, which is sandwiched between the liquid and the substrate, will highlight the textured surface.
When creating an optical system such as this, the refractive index of the reflective coating does not need to be the same as the other light transmitting materials for two reasons. First, the reflective coating is very thin, in the order of angstroms. Second, it has, for all practical purposes, an even thickness at all points across the surface. Because of the reflective coating's substantially uniform thickness, the optically clear liquid can very closely, if not perfectly, match the textured surface of the substrate. Because it is very thin, the optically clear liquid can come within angstroms of contacting the textured surface of the substrate. As a result of these two conditions, light is able to pass through the reflective coating practically undisturbed.
By observing these basic principals, an optical lens, such as used for sunglasses, can be made in such a way as to reflect light in a scattered manner, while at the same time transmit light in a coherent manner. Such a lens is advantageous in that on the face of an eyeglass lens, decorative patterns, images, logos, etc. can be made apparent to an observer while presenting no adverse affect to the wearer of the lens.
U.S. Pat. No. 4,315,665 describes an optical lens structure comprised of a first transparent layer that has a relief pattern on one surface, a reflective coating applied to the relief pattern, and a second transparent layer applied to the reflective coating. The second transparent layer is described as being applied in a manner that fills in the surface variations of the reflective coated relief pattern. The objective of the three-layer structure is to reflect a portion of incident light in the form of an image created by the relief pattern, while allowing the remainder of the incident light to pass undistorted. The reference further teaches that the first and second transparent layers are to have substantially the same refractive index. This reference is silent, however, as to the means by which this is to be accomplished. More specifcally, it does not teach any method by which the second transparent layer, having a similar refractive index as the first transparent layer, is adhered to the reflective coating. With regard to matching refractive indices, as described, the problem encountered is that lens elements that serve as structural substrates, such as thermo or thermoset plastics, typically do not have the inherent capability to adhere to materials such as those typically employed as reflective coatings. Therefore, to create a lens structure of the type described in this prior art reference, manufacturers typically rely on adhesives or epoxies to bond a second preformed transparent layer to the reflective coating. The term "preformed" relates to the idea of the transparent layer being a solid state substrate, such as a sheet of plastic, wherein the sheet is adhered to the adhesive by means of lamination.
The foregoing reference describes holography as being a suitable means for creating a surface relief pattern that will reflect images and or decorative light patterns. Moreover, holography is described as being the method of choice. Today, eyeglasses with holographic images on the eyeglass lenses are commonly available. These types of eyeglasses are typically considered to be novelty items. Adhesives are typically employed in manufacturing the holographic lenses used in these eyeglasses. An adhesive is applied to the surface of the reflective coating to facilitate transmission of light through the lens as well as to provide a binary layer to which an additional preformed transparent layer can be applied. The additional preformed transparent layer protects the adhesive, the reflective coating, and the holographic relief pattern upon which the reflective coating is applied. The problem encountered when incorporating adhesives or epoxies, as described, is that bonding elements inherently cause optical distortion. The resulting distortion of light is directly proportional to the degree to which the surface of the substrate, upon which the adhesive or epoxy is applied, is textured or contoured. The descriptive terms "textured" and "contoured" are in reference to prior art in which surface relief patterns and surface variations are described. The main reason the bonding elements cause optical distortion is because of a mismatch in refractive indices. The material used to create the first transparent layer, having the surface relief pattern thereon, is not the same type of material used to bond the elements together. Because the materials are not the same, for all practical purposes, there will always be a mismatch in refractive indices. The reason the mismatch is a problem is because the bonding element is the material used to fill in the peaks and valleys of the surface relief pattern. If the surface relief pattern is created by holographic means, the subject of mismatched refractive indices is less of a problem. This is because the peaks and valleys comprising the surface variations typically have a depth of about 0.5 to 1.0 microns. As previously mentioned, the distortion due to a mismatch in refractive indices is directly proportional to the degree to which the surface of the substrate, upon which the adhesive or epoxy is applied, is textured or contoured. That is, the less the surface is altered, the less light will be distorted when passing through the altered surface, and the less the bonding element will have to work to restore the direction of the distorted light rays. Nevertheless, sunglasses incorporating holographic lenses historically have exhibited very poor optical clarity. This, more than anything else, is why holographic sunglasses are considered to be novelty items.
U.S. Pat. No. 5,464,710 describes a holographic sheet construction that can be utilized as an eyeglass lens. The manner in which the sheets are assembled is very similar to the methods described above in which an adhesive is applied. In another embodiment described in this reference, an acrylate type material is applied to the reflective coating instead of using a preformed transparent layer to protect both the adhesive and the reflective coating. The acrylate coating is taught to be approximately 1.5 to 5.0 microns thick, which is just thick enough to fill in the peaks and valleys of the surface relief pattern. The top coat is taught to serve as a protective coating for the reflective coating as with the adhesive coating. The same problem exists with the acrylate protective coating, that is, the material used to create the substrate, described as a polyester substrate, upon which the surface relief pattern is applied, is not the same as the material used to create the protective coating.
U.S. Pat. No. 4,934,792 to Tovi, describes a lens structure similar to those of the prior art previously described. This reference teaches a first lens element having a surface relief pattern on one surface, a reflective medium applied to the surface relief pattern, and a second lens element applied to the reflective coating. The second lens element is described as having a refractive index substantially similar to the first lens element. The only method taught for adhering the second lens element to the reflective coating is by means of an adhesive. The use of an adhesive, however, would negate any advantage gained by ensuring that the second lens element has a refractive index similar to that of the first lens element. Because the adhesive is between the reflective medium and the second lens element, the second lens element is displaced from the reflective coated relief pattern. The second lens element is displaced by the adhesive layer because the adhesive layer will fill in the peaks and valleys of the reflective coated relief pattern. This reference does, however, recognize this inherent problem in stating that such a method would not be practical if the refractive index of the adhesive cannot be matched to the refractive index of the other lens elements. To further complicate the problem of optical distortion, as previously described, the surface relief patterns described in this reference have peaks and valleys that far exceed the depth of those created by holographic relief patterns. As an example of a relief pattern, Tovi teaches use of the face of a coin, such as a silver dollar, against which a plastic material is cast. The resulting distortion of light created by such a relief patterns is far greater than that created by a holographic image. Therefore, it would be anticipated that the resulting optical clarity of such a lens structure would be worse than that of a holographic type lens structure of the type previously described.
U.S. Pat. No. 5,073,009, also to Tovi, suggests an alternative method of construction of a lens structure in which a first layer of plastic or adhesive material is cast upon a preformed transparent lens element. It is suggested that the plastic or adhesive material be a type that can be poured, such as polycarbonate, acrylic or polyester. The surface of the plastic or adhesive material, opposite the first preformed transparent lens element, has a surface relief pattern thereon. The nature of the adhesive or plastic material is such that it adheres to the first lens element. The surface relief pattern, such as the face of a coin, against which the plastic or adhesive material is cast, is covered with metal foil. After the first layer of adhesive or plastic material has cured, the metal foil is removed from the surface, revealing the surface relief pattern of the coin. A reflective coating, such as a thin layer of aluminum, is then applied to the surface of the relief pattern. A second layer of plastic or adhesive material, similar to that used to create the first layer of plastic or adhesive, is then poured onto the reflective coating. Prior to curing the second plastic or adhesive layer, a second preformed transparent lens element is pressed against the uncured plastic or adhesive layer, thereby creating a sandwiched lens structure. Tovi does not specifically teach how the elements of the lens structure are bonded together. For example, it is stated that the plastic or adhesive material used to create the first layer is to be similar to the plastic or adhesive material that is poured onto the reflective coating. If the second layer of adhesive or plastic material is capable of bonding to the aluminum reflective coating, it would be anticipated that the plastic or adhesive material, used to create the first layer, would bond to the object providing the surface relief pattern, such as the metal foil. Nevertheless, this method of construction is overly complex and not suitable for a production environment.
U.S. Pat. No. 4,715,702 to the present inventor describes a decorative lens that includes a reflective mirror type coating sandwiched between two decoratively printed light transmitting substrates. The idea is to print a first transparent colored pattern onto a clear substrate and then apply a semi-transparent mirror coating over the printed pattern. A second transparent colored pattern is printed over the top of the mirror coating. The second pattern is a negative of the first pattern. The objective of the second printed pattern is to cancel the pattern created by the first printed pattern. In the final lens structure, the reflective coating highlights the un even texture of the printed decorative pattern. The resulting textured finish of the reflective coating gives the lens a favorabley unique appearance from an observer's point of view, while being relatively transparent from the wearer's point of view. The final lens structure, however, tends to distort transmitted light and, therefore, does not exhibit the optical quality of a conventional lens. It has been subsequently determined that the light was distorted because the refractive index of the transparent decorative pattern was different than the refractive index of the adhesive that was used to hold the multilayer lens structure together. At this point, it became apparent that an improved method of construction of a lens with a textured coating was needed, that is, a method that would not inherently cause distortion.
With regard to holographic eyeglasses, the manner in which the images are made visible is by reflecting different colors in the form of the given image. Prior art holographic eyeglasses all have, for the most part, one thing in common, eyeglass lenses that brightly reflect images and or objects. For example, holographic eyeglasses that reflect images of steel nails, eyeballs, broken glass, skulls and faces are some of the most common types. U.S. Pat. Nos. 5,073,009 and 4,934,792 describe surface relief patterns depicting the face of a coin and patterns created from photographs. U.S. Pat. No. 4,715,702 teaches the creation of images of stars, circles, and stripes. In accordance with the present invention, a more aesthetically pleasing lens structure can be implemented by creating a lens that reflects light but does not reflect an image. The present invention describes lens structures, and methods of making the same, that are not only optically superior to those of the prior art, but considered to be more aesthetically appealing to consumers.
U.S. Pat. No. 4,873,029 describes a tinted plastic lens having a plastic protective coating applied to the surface(s) thereof. The objective of the protective plastic coating is to protect the tint from abrasion. Also, the plastic layer is described as being useful for creating prescription multi-focal lenses. A pretinted lens element, referred to as a wafer, is placed inside a mold cavity that is larger than the wafer. The mold cavity is then filled with a liquid monomer. The liquid monomer is cured by heat, thereby forming a protective layer over the lens wafer. In another embodiment, a tinted plastic lens has a plastic coating cast onto one surface of the first lens. As before, the plastic coating is employed to protect the tint from abrasion as well as to provide a prescription or multi-focal element. U.S. Pat. Nos. 5,147,585 and 5,219,497 describe methods of creating multi-focal and progressive lenses by casting an additional plastic element onto one surface of a preformed plastic lens and curing the additional plastic element by both heat and ultraviolet light. U.S. Pat. Nos. 5,512,371 and 5,702,819 describe a multi-element lens structure combining a polycarbonate lens element with an allyl diglycol lens element wherein surface casting methods, similar to those described in U.S. Pat. Nos. 5,147,585 and 5,219,497 are used to create multi-focal lenses, progressive lenses or nonprescription lenses. The lenses taught in U.S. Pat. Nos. 5,147,585 and 5,219,497 combine the scratch resistance of allyl diglycol carbonate and the impact resistance of polycarbonate. These lenses relate to the lenses of the present invention only in that they employ additional lens elements formed on a preformed lens element. These prior art references do not describe the use of additional adhesion promoting elements, nor do they describe the use of reflective mediums. The function, appearance, and objectives of the lens structures disclosed in these references are not at all like the lens structure of the present invention.
U.S. Pat. No. 5,757,459 describes a method for forming a lens by injection molding a thermoplastic, referred to as the power portion, onto a multi-element laminated sheet structure. The power portion is taught to be a material such as polycarbonate, while the laminated sheet structure, which is referred to as a functional portion, is of a type that is polarized or photochromic. This reference teaches a lens that combines a thermoplastic lens form with a functional portion, wherein the lens can be fabricated as a semifinished lens, a prescription lens or a non-prescription lens. Ordinary acrylic epoxy, and urethane type adhesives are employed to create the function portion. These adhesives are incompatible with the method of the present invention. Furthermore, this prior art reference does not teach any type of reflective medium. The function, appearance, and objectives of the lens structure disclosed in this reference are not at all like the lens structure of the present invention.